Electric furnace



Dec. 25, 1928. 1,696,728

A. N. oTls n AL ELECTRIC FURNACE File@ Sept. 10, 1925 2 Sheets-Sheet l M Figi.

Invent ors I 2m 272/ Carl Llpsem Albert N.'Ots,

by M5L@ Their` Attorng.

A. NQOTIS ET AL D@n 25, 192s.

ELECTRIC FURNACE Filed sept. 1o, 1925 2 *Sheets-Sheet 2 by A.

Their Attorney.

.Patented Dec. 225,' '1928.

' UNITED STATES PATENT OFFICE.

ALBERT N. OTIS AND CARL L. IPSEN, OF SCHENECTADY, NEW YORK, .ASSIGNOBS T0 GENERAL ELECTRIC COMPANY, A. CORPORATION OF NEW YOB.

ELECTRIC FUnNAcE.

Application led September 10, 1925. Serial No. 55,585.

Our invention relates to electric furnaces or ovens employing resistance heaters or re-` sistors, and has for its object the provision of an improved arrangement and construction which is particularly adapted for caiiying out various heating operations.

Our invention has particular application in the heatin of attenuated articles, such as mine drills, orgings, etc. In carrying out our invention we provide a plurality of relatively small furnace openings through which the parts to be heated may be inserted and arrange the heating resistor around these openings so as to be in close proximity to the work and radiate heat to the work from all directions. In one form of our invention we shape the resistor into a plurality of loops or convolutions substantially filling or coextensive with the heating chamber and provide openings through which the articles to be heated may be inserted between the convolutions.

For a more complete understanding of our invention reference should be had to the accompanying drawing in which Fig. 1 is a side elevation view of an electric furnace embodying our invention; Fig. 2 is a transverse vertical sectional view of the device shown in Fig. 1, while Figs. 3 and 4 are fragmentary nace in accordance with one form of our in.

vention is provided with an elongated heating chamber which is defined by walls built up from heat refractory bricks 10, the whole being in a suitable metallic casing l1, and mounted on a suitable base 12. A plurality of relatively small openings 13 leading into the heating chamber are lprovided along one side, these openings being of the size suitable to permit the insertion of the article to be heated freely therethrough into the interior of the furnace chamber. As shown, the openings 13 may be defined by tubular heat refractory members 14 which are built into the side walls of the furnace, a suitable powdered heat refractory material 15 being provided around the -outer ends of the tubes 14. A metallic plate 16 is mounted on the side of the furnace and provided with openings corresponding to the openings 13 of the furnace, these openings being countersunk as shown at. 17 on the inner side of the plate to receive the outer ends of the tubes 14 so as to support them.

At intervals along the tops of the side walls of the furnace specially constructed bricks are inserted provided with recesses 18 in which the ends of a plurality of transverse .bei' so that ledges 22 and 23 remain, a central ledge 24 being formed grooves.

The furnace is heated by means of a ribbon shaped resistor which is draped or hun@ over the transverse rods 19 so as to hang ownward in a series of V-shaped loops or convolutions between the rods, and laid in zigzag formation on the ledges 22, 23 and 24 at the bottom of the furnace. In the arrangement shown the resistor is divided into two sections 25 and 26, each section, consisting of a top or overhead series of loops and a bottom series of loops, ex ending the full length of the heating chamber. These two sections have their ends connected together in parallel relation and brought out at one end of the furnace to the terminals 27 and 28 whereby they may be connected in parallel to a suitable source of electrical supply. The two upper portions 25n and 26a are connected at one end to the terminal 28 and have their opposite ends connected respectively to the coi'- responding ends of the bottom portions 25b and 26" which extend the full length of the furnace and are connected to the terminal 27.

The bottom portions 25b and 26" are similar in shape to the top portions but are laid flatwise or horizontally on the ledges 22, 23 and 24, i. e., the bottom portions rest on their edges on these ledges. In the arrangement shown, the bottom portion 25b extends back and forth between the ledges 22 and 24 with its bends resting lon the ledges and the porbetween the two electrically insulating tion 261 rests in a similar manner on the arranged alsov so thattheir bends occur in the same vertical transverse plane of the furnace, as shown in detail in Fig. 4, the zigzag lengths of the bottom portions being parallel. rIhis4 arrangement provides for the maximum spacing of the bottom portions. ln order to maintain this spacing and'assure that the bottom portions do not come in contact with each other, notches 29 are cut in the ledges .22, 23 and 24 in which the bends are laid. Preferably the front section 26 is made somewhat heavier so that its rate of heat gener-ation will be hi her to `compensate for the loss of heat throug the openings 13. A

With this arrangement of the heating resistor it 'will be observed that heat is radiated from all directions to the tools inserted through the openings 13. This will be apparent from an examination of Fig. 3 inl which a mine drill-30 is v shown in the position relative to the heating resistor which it would have when inserted through one of the openings 13. The depending loops 31 of the top portions of the two sections hang down between thel opening`l3, 'as 'shown in Fig. 1, so that the work pieces are inserted between these loops, and between the top and bottom portions, so as to be brought in close proximity to the heating resistor. It will be observed that the loops of the resistor substantially fill or are coextensive with the heating chamber, in fact the loops of the upper portions alone substantially fill the chamber, the top and bottom portions being in close proximity to each other, and the work pieces being inserted, as previously noted between these portions and between the loops of the top portion. The arrangement of the supports for the resistor, i. e., the bars 19`and the ledges 22, 23 and 24 are such that the resistor issupported with a very small area of contact between the resistor and the supporting parts. This provides for eliicient radiation of heat from the resistor, prevent-- ing local overheating at the points of support. Furthermore, the horizontal arrangement of the lower portions allows the scaleto drop through into the troughs 20 and 21 without short-circuiting portions of the resistor. The particular.- arrangement shown provides an exceedingly rugged and reliable construction.

In accordance with the provisions of the patent statutes We have described the principle of operation of our invention, together with the ap-paratus which we now consider.

to represent the best embodiment thereof, but we desire to have it understood 'that thel apparatus shown and described is only illustrative and that the invention may be carried out by other means. l f

What we claim as new and desire to secure by Letters Patent of the United States is parallel bars extending across said chamber.

having their ends secured in opposite walls, and a heating resistor hung from said bars in a series of depending loops.

2L An electric furnace comp-rising side and end walls forming a heating chamber, a heating resistor in said chamber arranged in a plurality of loops extending lengthwise of said chamber, said side walls being provided with a plurality of apertures through which the articles to be heated can be inserted between said loops.

3. An electric furnace for heating attenuated articles comprising side and end heat refractory walls forming a heating chamber, and a heating resistor in said chamber provided with a plurality of loops extending from one end of said chamber to the other, one of said side walls being provided with a plurality of apertures through which the articles to be heated can be inserted between said loops. l 4. An electric furnace for heating attenuated members comprising heat refractory walls forming an elongated furnace chamber provided-with a plurality of relatively small side openings, and a heating resistor extending lengthwise of said chamber arranged in a plurality of loops hanging between sai-d openings.

5. An electric furnace comprising heat refractory wallsI forming an elongated furnace chamber provided with a plurality of relatively small side openings, a heating resistor extending lengthwise of said chamber arranged in a plurality of loops hanging between said openings. a. plurality of bars extending across said chamber forming supports for said resistor, and a sinuous resistor on the bottom of said chamber below said openings said resistors being arranged in said chamber for direct radiation to the work inserted through said apertures.

6. An electric furnace comprising side and end heat refractory walls forming a. furnace chamber, l*one of: said side Walls being provided with a plurality ofrelatively small openings, a pluralit of insulating bars extending across said c amber from side to side thereof, and a heating resistor hanging from said bars in a series of loops arranged between said opening.

1. An electric furnace comprising side and end heat refractory walls forming a heating chamber, a resistor shapedfinto a; series'of vertical loops and a series of horizontal loops extendinggffrom one end -of the chamber to the other, said side walls being provided with apertures through which the articles to be' heated can be inserted between said series of vertical and horizontal loops and between said vertical loops.

ico

fractory Walls forming an elongated heating extending lengthwise of said chamber supohamber provided with a plurality of relaported on said bars and ledges. tively small side openings, a plurality of bars In witness whereof we have hereunto set 10 of insulating material extending across -the our hands this 9th day of September, 1925.

5 top of said chamber, spaced ledges on the bottom 0f Said chamber extending length- ALBERT N.` OTIS. Wise thereof, and a sinuous heating resistor CARL L. IPSEN. 

